Polyester fiber cord for reinforcing rubber

ABSTRACT

A polyester fiber cord for reinforcing rubber including a polyester fiber preloaded with a polyepoxide compound; and an adhesive applied to the polyester fiber and including a resorcinol-formalin-rubber latex (A), a blocked polyisocyanate compound (B), and a halogenated phenol derivative (C), wherein a rubber latex, a material of the resorcinol-formalin-rubber latex (A) in the adhesive, contains a mixture of a chloroprene rubber latex (D) and a polybutadiene rubber latex (E) in an amount of 80 to 100 parts by mass based on 100 parts by mass of the total solids of the rubber latex, and a mixing ratio of the chloroprene rubber latex (D) to the polybutadiene rubber latex (E) ((D)/(E)) is 80/20 to 20/80 (solid content mass ratio).

TECHNICAL FIELD

This disclosure relates to a polyester fiber cord for reinforcing rubber and, particularly, relates to a polyester fiber cord for reinforcing rubber having good adhesion to an ethylene-α-olefin-unconjugated diene copolymer rubber formulation (hereinafter referred to as “EPDM rubber”) and improved processability in manufacturing a product such as an automotive hose, i.e., coming off of resorcinol-formalin-rubber latex (which hereinafter may be referred to as “RFL”) used as an adhesive on the polyester fiber cord surface.

BACKGROUND

Polyester fibers represented by polyethylene terephthalate fiber have been used as a reinforcing fiber for rubber hose due to their physical properties such as high tenacity, high modulus, low elongation, being less prone to creep, and high fatigue resistance. However, the polyester fibers have a problem of poor adhesion to rubber resulting from their inactive surface. In recent years, EPDM rubber with excellent high-temperature properties has been mainly used in the field of hoses used as automotive hoses such as brake hose and air-conditioner hose, but this rubber has a problem of poor reactivity due to its chemical structure with a small number of double bonds. Accordingly, various methods have been investigated to improve the adhesion of a polyester fiber cord to EPDM rubber.

On the other hand, there is a problem in that when a plurality of fiber cords provided with an adhesive is aligned and braided into a hose shape or when a cord provided with an adhesive is rubbed against guides, coming off of the adhesive, adhesion to the guides, and scattering occur, compromising productivity and the work environment.

Attempting to solve the above problems, a method is disclosed in which a polyester fiber preloaded with a polyepoxide compound is treated with a treatment comprising a resorcinol-formalin-rubber latex and a chlorophenol compound (JP 2008-7929 A). Further, a method is disclosed in which a polyester fiber preloaded with a polyepoxide compound is treated with a treatment comprising a resorcinol-formalin-rubber latex comprising modified VP and a chlorophenol compound (JP 2008-202182 A). Further, a method is disclosed in which a polyester fiber is treated with a first treatment comprising a polyepoxide compound and a vinylpyridine-styrene-butadiene-rubber latex, and then treated with a second treatment comprising a resorcinol-formalin-rubber latex and a chlorophenol compound (JP 07-216755 A). Further, a method is disclosed in which a polyester fiber preloaded with a polyepoxide compound is treated with a second treatment comprising a resorcinol-formalin-rubber latex comprising specific vinylpyridine-styrene-butadiene and a chlorophenol compound (JP 07-331583 A). Furthermore, a method is disclosed in which a polyester fiber is treated with a first treatment comprising a polyepoxide compound, and then treated with a second treatment comprising a resorcinol-formalin-rubber latex of a specific composition and a chlorophenol compound (JP 11-286875 A).

These methods are effective to some degree with respect to adhesion to EPDM rubber, but a polyester fiber cord for reinforcing rubber having good processability in a manufacturing process cannot be obtained at present.

It could therefore be helpful to provide a polyester fiber cord for reinforcing rubber having good adhesion to an ethylene-α-olefin-unconjugated diene copolymer rubber formulation (EPDM rubber) and improved processability in manufacturing a product such as an automotive hose (coming off of RFL on the polyester fiber cord surface).

SUMMARY

We thus provide a polyester fiber cord for reinforcing rubber, comprising a polyester fiber preloaded with a polyepoxide compound, and an adhesive applied to the polyester fiber, the adhesive comprising a resorcinol-formalin-rubber latex (A), a blocked polyisocyanate compound (B), and a halogenated phenol derivative (C), wherein a rubber latex, a material of the resorcinol-formalin-rubber latex (A) in the adhesive, contains a mixture of a chloroprene rubber latex (D) and a polybutadiene rubber latex (E) in an amount of 80 to 100 parts by mass based on 100 parts by mass of the total solids of the rubber latex, and the mixing ratio of the chloroprene rubber latex (D) to the polybutadiene rubber latex (E) ((D)/(E)) is from 80/20 to 20/80 (solid content mass ratio), and a method of producing the same.

For the polyester fiber cord for reinforcing rubber, (1) to (9) below are preferred, and satisfaction thereof can produce a more excellent effect.

(1) The chloroprene rubber latex (D) has a surface tension of 30 to 44 mN/m and, desirably, an average particle size of 50 to 200 nm.

(2) The polybutadiene rubber latex (E) has an average particle size of 200 to 330 nm.

(3) The polyester fiber preloaded with a polyepoxide compound has an amorphism degree of orientation (fa) of 0.45 to 0.65.

(4) The polyester fiber cord for reinforcing rubber is obtained by a single bath process where the polyester fiber preloaded with a polyepoxide compound is provided with the adhesive and then subjected to drying/heat treatment, and the total stretching rate in the drying/heat treatment is −10% to −4%.

(5) A resorcin-formaldehyde precondensate contained in the resorcinol-formalin-rubber latex (A) is a novolac-type condensate.

(6) The adhesive satisfies the following requirements about blend ratio:

(A)/(B)=5/1 to 20/1, (A)/(C)=1/1 to 5/1

(wherein (A) represents the amount of the resorcinol-formalin-rubber latex; (B) represents the amount of the blocked polyisocyanate compound; and (C) represents the amount of the halogenated phenol derivative, the ratios both representing a blend ratio by solid content mass).

(7) The total solids concentration of the adhesive is 3 to 15% by mass, and the deposited amount of solid content of the adhesive on the polyester fiber preloaded with a polyepoxide compound is 1.0 to 5.0% by mass based on 100% by mass of the polyester fiber preloaded with a polyepoxide compound.

(8) The polyester fiber cord for reinforcing rubber is a cord for reinforcing an automotive hose.

(9) In the automotive hose, at least a portion in contact with the polyester fiber cord for reinforcing rubber is an ethylene-α-olefin-unconjugated diene rubber formulation.

Thus, we enable satisfaction of both adhesion to EPDM rubber and good processability in a manufacturing process that have been unattainable in conventional polyester fiber cords for reinforcing rubber by adding a chloroprene rubber latex and a polybutadiene rubber latex in an amount within a specific range.

In other words, we provide a polyester fiber cord for reinforcing rubber having better adhesion to EPDM rubber and more improved processability in manufacturing a product such as an automotive hose (less coming off of RFL on the polyester fiber cord surface) than those of conventional polyester fiber cords for reinforcing rubber.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic view illustrating a friction tester that evaluates processability of a fiber cord.

DESCRIPTION OF SYMBOLS

-   -   1: Fiber cord sample for measurement     -   2: Yarn guide nip roller     -   3: Load     -   4: Chrome-plated textured roll     -   5: Yarn guide nip roller

DETAILED DESCRIPTION

For the polyester fiber cord for reinforcing rubber (hereinafter referred to as the cord), as a result of intensive studies to create a cord industrially practical in automotive hose applications, in particular, automotive brake hose or automotive air-conditioner hose applications, a polyester fiber cord for reinforcing rubber was obtained having both good adhesion to EPDM rubber and good processability with an RFL adhesive being less likely to come off the cord during hose production.

Our polyester fiber cords will now be described in detail.

A preferred polyester fiber is a polyester made from a dicarboxylic acid and a glycol. Examples of the dicarboxylic acid component include terephthalic acid, 2,6-naphthalene dicarboxylic acid, isophthalic acid, and 1,4-cyclohexanedicarboxylic acid. Examples of the glycol component include ethylene glycol, propylene glycol, tetramethylene glycol, and 1,4-cyclohexanedimethanol. The above dicarboxylic acid component may be partially replaced with adipic acid, sebacic acid, dimer acid, sulfonic acid, metal-substituted isophthalic acid, and the like, and the above glycol component may be partially replaced with diethylene glycol, neopentyl glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, polyalkylene glycol, and the like. Of these, preferred is a polyethylene terephthalate in which terephthalic acid accounts for 90 mol % or more of the dicarboxylic acid component and ethylene glycol accounts for 90 mol % or more of the glycol component. To this polyester, conventional antioxidants, sequestering agents, ion-exchange agents, stain inhibitors, waxes, silicone oil, and various surfactants as well as particles such as various inorganic particles, for example, of titanium oxide, silicon oxide, calcium carbonate, silicon nitride, clay, talc, kaolin, and zirconium acid, cross-linked polymer particles, and various metal particles may be added.

The polyepoxide compound is a compound having at least two epoxy groups in one molecule. The amount of epoxy group is preferably at least one per 1000 g of the polyepoxide compound (i.e., the epoxy equivalent weight is 1000 g/eq or less). Specific examples include reaction products of a polyhydric alcohol such as pentaerythritol, ethylene glycol, polyethylene glycol, propylene glycol, glycerol, or sorbitol and a halogen-containing epoxide such as epichlorohydrin; and polyepoxide compounds obtained by oxidizing an unsaturated compound with a peroxide, hydrogen peroxide or the like: i.e., compounds such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexene carboxylate, and bis(3,4-epoxy-6-methyl-cyclohexylmethyl)adipate; aromatic polyepoxides such as phenol novolac-type, hydroquinone-type, biphenyl-type, bisphenol S-type, brominated novolac-type, xylene-modified novolac-type, phenol glyoxal-type, trisoxyphenylmethane-type, trisphenol PA-type, and bisphenol-type polyepoxides; and the like. Particularly preferred are sorbitol glycidyl ether-type and cresol novolac-type polyepoxides.

These compounds are typically used as contained in an emulsified liquid. To form an emulsified liquid or a solution, the polyepoxide compound can be mixed as it is with a liquid to form an emulsified liquid or a solution. The polyepoxide compound can optionally be dissolved in a small amount of solvent, and the resultant can be mixed with a liquid together with an emulsifier such as sodium alkyl benzene sulfonate, sodium dioctyl sulfosuccinate, or a nonylphenol ethylene oxide adduct to obtain an emulsified liquid or a solution.

The polyepoxide compound is typically applied together with a spinning lubricant during the process for spinning the polyester fiber. The deposited amount of the polyepoxide compound in this case is typically 0.1 to 5% by mass based on the polyester fiber. When the deposited amount of the polyepoxide compound is less than 0.1% by mass, the effect of the polyepoxide compound may not be fully exerted, not providing satisfactory adhesion between the polyester fiber and EPDM rubber. When the deposited amount of the polyepoxide compound is more than 5% by mass, the fiber may become very stiff, leading to difficulty in application during the spinning process; in addition, the penetrability of an adhesive applied during or after the following process may decrease, resulting in reduced adhesion performance, which is not preferred.

The amorphism degree of orientation (fa) of the polyester fiber preloaded with a polyepoxide compound is preferably 0.45 to 0.65, more preferably 0.47 to 0.62, and still more preferably 0.50 to 0.60. If this value is small, the durability may be poor when used as an automotive hose, and when it is large, the adhesion may be poor.

Further, the polyester fiber preloaded with a polyepoxide compound used in the polyester cord for reinforcing rubber preferably has properties (a) to (c) below.

(a) Single yarn fineness: 3.6 to 5.5 dtex

(b) Intermediate elongation (elongation at a load of 4.0 cN/dtex): 4 to 6%

(c) Dry heat shrinkage (ΔS): 2 to 14%

The single yarn fineness of the polyester fiber is preferably 3.6 to 5.5 dtex, more preferably 4.0 to 5.3 dtex. A single yarn fineness of less than 3.6 dtex leads to difficulty in stable spinning, and a single yarn fineness of more than 5.5 dtex may lead to reduced adhesion.

“Intermediate elongation” as used herein refers to an elongation at a load of 4.0 cN/dtex. Its value is preferably 4 to 6%, more preferably 4.3 to 5.7%. When seeking to achieve an intermediate elongation of less than 4%, it is difficult to achieve the desired dry heat shrinkag. An intermediate elongation of more than 6% may result in reduced pressure resistance in the use for reinforcing an automotive hose.

The dry heat shrinkage of the polyester fiber is preferably 2 to 14%, more preferably 4 to 12%. When seeking to provide a fiber with a low shrinkage, it is difficult to keep the intermediate elongation within the range described above. Too high a shrinkage may lead to reduced adhesion.

The cord comprises a polyester fiber preloaded with a polyepoxide compound, and an adhesive applied to the polyester fiber, the adhesive comprising a resorcinol-formalin-rubber latex (A), a blocked polyisocyanate compound (B), and a halogenated phenol derivative (C).

“Resorcinol-formalin-rubber latex” as used herein refers to a mixture of a precondensate of resorcin and formaldehyde with a rubber latex. The resorcin-formaldehyde precondensate is a substance obtained by condensation of resorcin and formaldehyde in the presence of an alkaline catalyst or acid catalyst, and the molar ratio of resorcin (R) to formaldehyde (F) is preferably 1/0.5 to 1/3, more preferably 1/1 to 1/3. A molar ratio R/F outside the above range may lead to reduced adhesion or poor processability.

Further, a novolac-type resin obtained by preliminarily reacting dihydroxybenzene with formaldehyde without catalyst or in the presence of an acidic catalyst can also be used as a resorcin-formaldehyde precondensate. Specifically, for example, a compound obtained by condensation of 1 mol of resorcin and up to 0.7 mol of formaldehyde can be used. Examples of the compound include “SUMIKANOL” 700(S) (trade name) (registered trademark) available from Sumitomo Chemical Co., Ltd. When such a compound in which the amount of formaldehyde is less than that of resorcin is used and it is desired to adjust the molar ratio of resorcin (R) to formaldehyde (F) to be within the more preferred range described above, it is preferable to dissolve such a novolac-type condensate of resorcin and formaldehyde in water containing an alkaline catalyst and then add formaldehyde to adjust the molar ratio of resorcin to formaldehyde to 1/1 to 1/3. The alkaline catalyst used here is preferably an alkali metal hydroxide, more preferably sodium hydroxide. The concentration of the water dispersion of the alkaline catalyst may be about 1 to 10 molar concentration.

The rubber latex used in the resorcinol-formalin-rubber latex needs to comprise a chloroprene rubber latex (D) and a polybutadiene rubber latex (E). If they are not mixed, practical adhesion to EPDM rubber will not be exhibited.

The mixing ratio of the chloroprene rubber latex (D) to the polybutadiene rubber latex (E) ((D)/(E)) needs to be 80/20 to 20/80 at a solid content mass ratio, and is preferably 70/30 to 30/70, more preferably 60/40 to 40/60. Too high a ratio of (D)/(E) may lead to reduced adhesion, and too low a ratio of (D)/(E) may lead to poor processability.

In addition, a rubber latex other than the rubber latices described above may be used in combination. In this case, it is necessary that the mixture of the chloroprene rubber latex (D) and the polybutadiene rubber latex (E) be contained in an amount of 80 to 100 parts by mass based on 100 parts by mass of the total solids of the rubber latex. Too small a total mass of (D) and (E) may lead to reduced adhesion and poor processability.

Examples of rubber latices other than the chloroprene rubber latex (D) and the polybutadiene rubber latex (E) include natural rubber latex, styrene-butadiene rubber latex, ethylenically unsaturated acid-modified styrene-butadiene rubber latex, vinylpyridine-styrene-butadiene rubber latex, ethylenically unsaturated acid-modified vinylpyridine-styrene-butadiene rubber latex, acrylonitrile-butadiene rubber latex, chlorosulfonated polyethylene, and ethylene-propylene-unconjugated diene ternary copolymer rubber latex.

Examples of the ethylenically unsaturated acid used as a modifier to produce the ethylenically unsaturated acid-modified styrene-butadiene rubber latex and the ethylenically unsaturated acid-modified vinylpyridine-styrene-butadiene rubber latex listed above include, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and butenetricarboxylic acid; unsaturated dicarboxylic acid monoalkyl esters such as itaconic acid monoethyl ester, fumaric acid monobutyl ester, and maleic acid monobutyl ester; and unsaturated sulfonic acids and alkali salts thereof such as sodium sulfoethyl acrylate, sodium sulfopropyl methacrylate, and acrylamidopropane sulfonic acid. These can be used alone or in combination of two or more.

When the ethylenically unsaturated acid described above is used to modify a rubber latex, the carboxyl group of the ethylenically unsaturated acid may be introduced into the rubber latex by copolymerization of ethylenically unsaturated ester monomers or ethylenically unsaturated acid anhydride monomers, followed by hydrolysis. Examples of ethylenically unsaturated acid ester monomers and ethylenically unsaturated acid anhydride monomers in this case include mono-, di-, and tri-esters of unsaturated carboxylic acid such as acrylic acid, methacrylic acid, crotonic acid, cinnamic acid, itaconic acid, fumaric acid, maleic acid, and butenetricarboxylic acid; and maleic anhydride, and one of them or two or more of them are used.

The chloroprene rubber latex preferably has a surface tension of 30 to 44 mN/m, more preferably 33 to 42 mN/m. A surface tension outside this range may lead to reduced adhesion.

Further, the chloroprene rubber latex preferably has an average particle size of 50 to 200 nm, more preferably 100 to 180 nm. An average particle size outside this range may lead to reduced adhesion.

The polybutadiene rubber latex preferably has an average particle size of 200 to 330 nm, more preferably 260 to 310 nm. An average particle size outside this range may lead to poor processability.

Furthermore, the blend ratio (by solid content mass) of resorcin-formalin (RF) to rubber latex (L) in the resorcinol-formalin-rubber latex (RF/L) is preferably 1/3 to 1/15, more preferably 1/5 to 1/12, and still more preferably 1/7 to 1/10. A ratio of RF/L outside this range may lead to reduced adhesion or poor processability.

The blocked polyisocyanate compound, upon heating, releases a blocking agent to form an active isocyanate group. Examples of the blocked polyisocyanate compound include reactants of a polyisocyanate compound such as tolylene diisocyanate, m-phenylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, or triphenylmethane triisocyanate and a blocking agent such as a phenol (e.g., phenol, cresol, and resorcin), a lactam (e.g., ε-caprolactam and valerolactam), an oxime (e.g., acetoxime, methyl ethyl ketoxime, and cyclohexane oxime), or ethyleneimine. Of these compounds, aromatic polyisocyanate compounds blocked particularly with methyl ethyl ketoxime, and aromatic compounds of diphenylmethane diisocyanate are particularly preferably used.

The blocked isocyanate that can be used in the present invention preferably has a dissociation temperature of 140° C. to 180° C., more preferably 150° C. to 170° C. A dissociation temperature of less than 140° C. may lead to poor adhesion, and a dissociation temperature of more than 180° C. leads to a stiff cord, and the cord may have poor fatigue resistance when used for an automotive hose application.

The blend ratio of the resorcinol-formalin-rubber latex (A) described above to the blocked polyisocyanate compound (B) that can be used ((A)/(B)) is preferably 5/1 to 20/1 at a solid content mass ratio, more preferably 8/1 to 15/1. Too low a ratio of (A)/(B) may result in a stiff cord, and too high a ratio of (A)/(B) may lead to reduced adhesion.

Examples of the halogenated phenol derivative include condensates produced by condensation of a phenolic compound including a halogenated phenol compound and formaldehyde, and compounds including the Formula below as a principal component are preferred.

In the Formula, X represents Cl or Br; Y and Z each represents any one selected from Cl, Br, H, OH, and C₁-C₄ alkyl groups; and n represents an integer from 1 to 10.

In preparing such a halogenated phenol derivative, for example, a halogenated phenol compound such as p-chlorophenol, p-bromophenol, o-chlorophenol, or o-bromophenol is used as a starting material, among which p-chlorophenol and p-bromophenol are preferred, and in particular, p-chlorophenol is preferably used.

By condensing such a material with formaldehyde in the presence of an alkaline catalyst, or by reacting a material preliminarily in the presence of an acid catalyst and reacting the resulting condensate with formaldehyde in the presence of an alkaline catalyst, the halogenated phenol derivative can be prepared.

Further, the halogenated phenol compound described above can also be used in combination with any other phenolic compound and co-condensed with formaldehyde. Examples of other phenolic compounds include phenol, resorcin, o-cresol, p-cresol, p-tert-butylphenol, and 2,5-dimethylphenol. Of these, resorcin is particularly preferably used.

Specific examples of halogenated phenol derivatives include 2,6-bis(2′,4′-dihydroxy-phenylmethyl)-4-chlorophenol (e.g., “Casabond” available from Thomas Swan & Co., Ltd. and “Denabond” (registered trademark) available from Nagase Chemicals Ltd.), 2,6-bis(2′,4′-dihydroxy-phenylmethyl)-4-bromophenol, and 2,6-bis(2′,4′-dichlorophenylmethyl)-4-chlorophenol. In particular, those composed mainly of a chlorophenol compound having three or more benzene nuclei are preferably used in terms of adhesion and processability.

The blend ratio of the resorcinol-formalin-rubber latex (A) to the halogenated phenol derivative (C) represented by the above Formula ((A)/(C)) is preferably 1/1 to 5/1 at a solid content mass ratio, more preferably 3/1 to 5/1. Too low a ratio of (A)/(C) may result in a stiff cord, and too high a ratio of (A)/(C) may lead to reduced adhesion.

For the adhesive, resorcin (R) and formalin (F) are preferably aged under the aging conditions of 20 to 30° C. for 2 to 6 hours, more preferably for 3 to 5 hours. An aging time of less than 2 hours may lead to poor processability, and an aging time of more than 6 hours increases the viscosity of RF solution, which may lead to difficulty in uniform application of an RFL adhesive to a polyester fiber.

Further, RFL is preferably aged under the aging conditions of 20 to 30° C. for 14 to 35 hours, more preferably 16 to 30 hours. Aging conditions outside this range may lead to reduced adhesion.

A preferred method of producing the polyester fiber cord for reinforcing rubber will now be generally described.

Using o-chlorophenol as a solvent, polyethylene terephthalate chips whose intrinsic viscosity (IV) after 10 minutes at 145° C. is 1.00 to 1.50, preferably 1.20 to 1.50, are melt-spun with an extruder-type spinning machine at a spinning temperature of 285 to 300° C. After spinning, a treatment obtained by adding a polyepoxide compound into a spinning lubricant is applied with an oiling roller. Spinning is carried out at a speed of 2200 to 2800 m/min, and a spun yarn is subjected to a multistage hot stretching to a stretching magnification of 2.1 to 2.4, subjected to a relaxation of 1.0 to 4.0%, and then wound up to obtain a polyester fiber. The fineness and single yarn fineness of the polyester fiber are varied by varying the number of holes in a spinneret and the discharge rate. The hot stretching of the polyester fiber is carried out with a yarn wound up around a heating roll at 80 to 250° C.

The polyester fiber obtained as described above is twisted to obtain an untreated cord. The form of twist here may be single twist or organzine, but the polyester fiber cord for reinforcing rubber is preferably single twisted. The number of twists is preferably 5 to 20 t/10 cm, more preferably 8 to 18 t/10 cm. When it is less than 5 t/10 cm, a hose may have poor fatigue resistance, and when it is 20 t/10 cm or more, a cord may be crimped, leading to poor processability.

The untreated cord is then provided with the adhesive. The adhesive is preferably applied in the form of a treatment liquid obtained by dissolving or dispersing the adhesive in a liquid. The total solids concentration of the adhesive in the treatment liquid is preferably 3 to 15% by mass, more preferably 4 to 10% by mass. Within this range, the treatment liquid containing the adhesive is highly stable, and an RFL treatment can be uniformly applied to the polyester fiber.

To deposit the treatment liquid containing the adhesive on the polyester fiber, any method can be employed such as immersion, nozzle spraying, or application with a roller. For example, a computreater or a many weights type cord setter machine manufactured by Litzler Co., Inc. can be used for treatment.

The deposited amount of the adhesive on the polyester fiber preloaded with a polyepoxide compound is preferably in the range of 1 to 5% by mass, in particular, 1.5 to 3% by mass, at a dry mass ratio, and within this range, good adhesion to rubber and good processability are provided. The deposited amount of the adhesive can be controlled, for example, by adjusting the adhesive concentration or the conditions of liquid removal after immersion in an adhesive liquid.

Typically, the polyester fiber is provided with the adhesive, and then heat-treated. In the heat treatment, typically, drying is performed at 80 to 180° C. for 0.5 to 5 minutes, more preferably for 1 to 3 minutes, and then heat treatment is performed at 150 to 260° C., more preferably 220° C. to 250° C., for 0.5 to 5.0 minutes, more preferably for 1 to 3 minutes.

To control the physical properties of a cord and improve the adhesion, the drying is preferably carried out while applying a stretch of 0 to 1%. After applying the stretch of 0 to 1%, the heat treatment is preferably carried out while applying a relaxation of −10% to −5%, and the total stretching rate, the total of the stretching rate and the relaxation rate, is preferably −10% to −4%, more preferably −8% to −5%. When the total stretching rate is less than −10%, the cord may be loose, and it is difficult to perform a stable treatment. When it is more than −4%, the adhesive may be unevenly distributed at the outer layer of the cord, and the processability tends to be poor.

The polyester fiber cord for reinforcing rubber can be used as a cord for reinforcing various automotive hoses such as brake hose, air-conditioner hose, and fuel hose.

Further, in the case of the automotive hoses, it is preferred that at least a portion in contact with the polyester fiber cord for reinforcing rubber be an ethylene-α-olefin-unconjugated diene rubber formulation (EPDM rubber) since the desired effects can be maximized.

The shape and structure of the automotive hose may be any conventional one, but is not limited thereto. A structure is preferred in which a reinforcing fiber is wound up around inner layer rubber in one layer or two or more layers, and the reinforcing fiber is coated with outer layer rubber.

Examples of the method of winding up the reinforcing fiber cord include a braid knitting method in which one fiber cord and another fiber cord are wound up alternately for top and bottom, and a spiral knitting method in which one fiber cord is wound up and another fiber cord is wound up thereon. The reinforcing fiber cords may take any shape, and they may be in close contact with each other or may be separated from each other.

Vulcanization of the automotive hose is carried out under dry heat or under water vapor, typically, at 150° C. to 160° C. for 30 minutes to 1 hour, and conditions such as vulcanizing method, vulcanizing time, and vulcanizing temperature may be selected as appropriate.

EXAMPLES

Our polyester fiber, cords and methods will now be described in more detail by way of example, but this disclosure is not limited thereto.

The cord shape and the required properties of the cord for reinforcing rubber, and methods of measuring and evaluating physical properties are as described below.

Methods of Evaluating Polyester Fiber (Physical Properties) (1) Fineness

The total fineness was defined as a fineness based on corrected weight as measured by JIS L1013 (2010) 8.3.1 A method under a specified load of 0.045 cN/dTex.

(2) Single Yarn Fineness

A value obtained by dividing a fineness by the number of single fibers was employed.

(3) Tenacity, Intermediate Elongation

Measurements were made under the constant-rate-extension conditions shown in JIS L1013 (2010) 8.5.1 Standard Condition Test using “TENSILON” (registered trademark) UCT-100 manufactured by Orientec Co., Ltd. at a chuck distance of 25 cm and a tensile speed of 30 cm/min. Elongation was determined from an elongation at a point showing a maximum tenacity in an S-S curve. The intermediate elongation of an original yarn was defined as an elongation at a load of 4.0 cN/dtex (in the case of an original yarn with a fineness of 1100 dTex, an elongation (%) at 44 N was measured).

(4) Dry Heat Shrinkage

In accordance with JIS L-1013 (2010), 8.18.2 Dry Heat Shrinkage, a) Skein Shrinkage (A method), measurements were made at a specified load at sampling of 5 mN/tex×displayed tex number, a processing temperature of 150° C., and a specified load at skein length measurement of 200 mN/tex×displayed tex number.

(5) Amorphism Degree of Orientation (fa)

An amorphism degree of orientation (fa) can be determined from the equation below in R. S. Stein et al, J. Polymer Sci., vol. 21, p. 381 (1956) using birefringence, crystallinity determined from density, and crystal degree of orientation, and an average value of two measurements was calculated.

Δn=Xf _(c)Δ0c+(1−X)f _(a)Δ0_(a)

In the equation, Δn is a birefringence; X is a crystallinity; fc is a crystal degree of orientation (fc=0.980); fa is an amorphism degree of molecular orientation; Δ0_(c) is an intrinsic birefringence of a crystalline region; and Δ0_(a) is an intrinsic birefringence of an amorphous region (Δ0_(c)=Δ0_(a)=0.23).

As the birefringence, an average value of three trials obtained through measurement by the Berek compensator method using a POH polarizing microscope available from Nippon Kogaku K.K. was used. As the density, an average value of three trials obtained through measurement at 25° C. by the density gradient tube method using toluene as a light liquid and carbon tetrachloride as a heavy liquid was used. The crystallinity was calculated using the following equation.

Crystallinity(X)={dc(d−da)}/{d(dc−da)}

In the equation, dc is a crystal density (=1.455 g/cm³); da is an amorphous density (=1.335 g/cm³); and d is a sample density.

Methods of Evaluating Polyester Fiber Cord (Physical Properties) (1) Number of Twists

The number of twists was determined in accordance with JIS L1017 (2002) 8.4.

(2) Deposited Amount of Treatment

The deposited amount of a treatment was determined by the mass method of JIS L1017 (2002) 8.15 b).

(3) Cord Peel Adhesion

A cord was placed in parallel on an EPDM rubber sheet (5 mm thick) of the composition show in Table 1 (36 picks per inch (2.54 cm)), and press vulcanization was performed (150° C., 30 min, contact pressure between rubber and cord: 300 N/cm²). This sample was cooled to room temperature, after which a peel test was performed in which the cord was peeled off the rubber at a speed of 50 mm/min in an environment at 20° C. while maintaining the angle between the rubber and the cord at 90°. The force required at this time for peeling was expressed in N/2.54 cm.

TABLE 1 EPDM 100 Parts  HAF-Carbon black 90 Parts  Process Oil (Parffin group) 40 Parts  Zink oxide 5 Parts Stearic acid 5 Parts Actor PBM(*1) 4 Parts Accel TL-PT(*2) 3 Parts (*1)Product of Kawaguchi Chemical Industry Co,. LTD. (*2)Product of Kawaguchi Chemical Industry Co,. LTD.

(4) Processability

A cord was run through a friction tester manufactured by Toray Engineering Co., Ltd. shown in FIG. 1, and the state of adhesion of RFL debris to guides was used as an indicator. The fiber cord is supplied from a fiber cord sample for measurement 1, passed through a yarn guide nip roller 2, received a load 3, and run through a chrome-plated textured roll 4 partially wound around its surface. Further, the fiber cord is passed through a yarn guide nip roller 5 and taken up. The amount of RFL adhesion to the yarn guide nip roller 2 and the yarn guide nip roller 5 was measured. Evaluation results were expressed as follows: A: extremely low occurrence of debris, B: low occurrence of debris, C: high occurrence of debris, and ND: not able to be determined.

(5) Particle Size of Latex

A latex droplet was placed on a copper mesh for transmission electron microscope, the copper mesh being provided with a corrosion film, and stained with osmium tetraoxide, and then water was evaporated to dryness. A photograph was taken with a transmission electron microscope, and then the particle size was measured. For a non-spherical particle, the average of a major axis and a minor axis was used as its particle size. The particle size of the latex was defined as the arithmetic mean value of 50 measurements.

(6) Surface Tension of Latex

Measurements were made at 25° C. using a surface tension meter. A latex sample was placed in a container on a stage, and a well-washed platinum ring was immersed in the sample, after which the stage was gradually lowered, and a maximum load at the time when the ring was separated from the liquid level was detected and used as the value of surface tension. The average value of five measurements was employed.

Example 1

Into an aqueous caustic soda solution, a resorcin-formalin precondensate (“SUMIKANOL” 700(S) (registered trademark) (available from Sumitomo Chemical Co., Ltd., 65% aqueous solution)) was added and thoroughly stirred for dispersion. Formalin was added thereto so that the molar ratio of resorcin/formalin was 1/2, and the resulting mixture was uniformly mixed and aged at 25° C. for 4 hours to obtain a solution of resorcin-formalin condensate. Next, 60 parts by mass of a chloroprene rubber latex (“Shouprene” (registered trademark) 750 (available from Showa Denko K.K., surface tension: 39 mN/m, average particle size: 120 nm)) and 40 parts by mass of a polybutadiene rubber latex (“Nipol” (registered trademark) LX-111A (available from Zeon Corporation, average particle size: 300 nm)) were mixed to prepare a rubber latex mixture. The rubber latex mixture and the solution of resorcin-formalin condensate were mixed so that the solid content mass ratio of the former to the latter was 7/1, and the resulting mixture was aged at 25° C. for 24 hours to obtain a dispersion of resorcinol-formalin-rubber latex. Further, a halogenated phenol derivative (“Denabond E” (registered trademark) (available from Nagase Chemicals Ltd., 20% solution)) was added to the dispersion so that the solid content mass ratio of the former to the latter was 1/3, and the resulting mixture was thoroughly stirred and aged at 25° C. for 20 hours. Further, a blocked polyisocyanate compound (“ELASTRON” (registered trademark) BN27 (Dai-Ichi Kogyo Seiyaku Co., Ltd.)) was added to the mixture so that the solid content mass ratio of the resorcinol-formalin-rubber latex to the blocked polyisocyanate compound was 10/1, and the resulting mixture was thoroughly stirred to obtain a treatment liquid containing an adhesive. The concentration of the adhesive was 10% by mass.

Meanwhile, one multifilament of a polyester fiber (available from Toray Industries, Inc., T707M (1100 dTex) (single yarn fineness: 4.6 dTex, elongation at 44 N: 4.5%, dry heat shrinkage: 10.5%, amorphism degree of orientation: 0.55, 1100 decitex, 240 filaments; OriginalYarn A in Table 2), to which a polyepoxide compound (sorbitol polyglycidyl ether) was pre-applied by the method of applying a polyepoxide compound as a spinning lubricant in the spinning process, was single-twisted at 10 t/10 cm to obtain a twisted cord.

The cord was immersed in the treatment described above using a computreater (tire cord processor manufactured by C. A. LITZLER), dried at 120° C. under stretching conditions of 0% for 2 minutes, heat-treated at 240° C. under stretching conditions of 0% for 1 minute, and then heat-treated at 240° C. for 1 minute while being subjected to a relaxation of −6% (total stretching rate: −6%). The solid content of the treatment, i.e., the adhesive was deposited on the cord in an amount of 2.5% by mass. The cord thus obtained was evaluated for cord peel adhesion and processability as described above. The results are shown in Table 2.

Examples 2 to 10, Comparative Examples 1 to 6

The same procedure was repeated as in Example 1 except that the original yarn, latex, and total stretching rate used were changed as shown in Table 2 and Table 3, and evaluation was made in the same manner. Evaluation results are shown in Tables 2 and 3.

TABLE 2 Example Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 10 Original Yarn Original Original Original Original Original Original Original Original Original Original Yarn Yarn Yarn Yarn Yarn Yarn Yarn Yarn Yarn Yarn A A A A A A B A A A Latex Shouprene 750 60 75 45 45 40 25 60 60 60 — component Shouprene 115 — — — — — — — — — 60 LX111A 40 25 45 45 60 75 40 40 — 40 LX111NF — — — — — — — — 40 — Nipol 2518FS — — — — — — — — — — Nipol LX517B — — — 10 — — — — — — Total stretching rate −6% −6% −6% −6% −6% −6% −6% 0% −6% −6% Peel (N/2.54 cm) 135  114  128  125  137  133  94 105  115  115  adhesion Process- A A B B B B B B B A ability Shouprene 750: chloroprene rubber latex “Shouprene” (registered trademark) 750 (available from Showa Denko K.K.) Shouprene 115: chloroprene rubber latex “Shouprene” (registered trademark) 115 (available from Showa Denko K.K.) LX111A: polybutadiene rubber latex “Nipol” (registered trademark) LX-111A (available from Zeon Corporation) LX111NF: polybutadiene rubber latex “Nipol” (registered trademark) LX-111NF (available from Zeon Corporation) Nipol 2518FS: vinylpyridine-styrene-butadiene rubber latex “Nipol” (registered trademark) 2518FS (available from Zeon Corporation) Nipol LX517B: acrylonitrile-butadiene rubber latex “Nipol” (registered trademark) LX-517B (available from Zeon Corporation)

TABLE 3 Comparative Comparative Comparative Comparative Comparative Comparative Example Example Example Example Example Example 1 2 3 4 5 6 Original Yarn Original Yarn Original Yarn Original Yarn Original Yarn Original Yarn Original Yarn A A A A A A Latex Shouprene 750 100  90 30 30 10 — component Shouprene 115 — — — — — — LX111A — 10 30 30 90 100  LX111NF — — — — — — Nipol 2518FS — — 40 — — — Nipol LX517B — — — 40 — — Total stretching rate −6% −6% −6% −6% −6% −6% Peel adhesion (N/2.54 cm) 36 60 79 70 78 50 Processability ND ND C ND ND C Shouprene 750: chloroprene rubber latex “Shouprene” (registered trademark) 750 (available from Showa Denko K.K.) Shouprene 115: chloroprene rubber latex “Shouprene” (registered trademark) 115 (available from Showa Denko K.K.) LX111A: polybutadiene rubber latex “Nipol” (registered trademark) LX-111A (available from Zeon Corporation) LX111NF: polybutadiene rubber latex “Nipol” (registered trademark) LX-111NF (available from Zeon Corporation) Nipol 2518FS: vinylpyridine-styrene-butadiene rubber latex “Nipol” (registered trademark) 2518FS (available from Zeon Corporation) Nipol LX517B: acrylonitrile-butadiene rubber latex “Nipol” (registered trademark) LX-517B (available from Zeon Corporation) Original Yarn B: polyester fiber (available from Toray Industries, Inc., T707C (1100 dTex) (single yarn fineness: 5.7 dTex, elongation at 44 N: 4.2%, dry heat shrinkage: 15.5%, amorphism degree of orientation: 0.70, 1100 decitex, 192 filaments)) to which a polyepoxide compound (sorbitol polyglycidyl ether) is pre-applied as a spinning lubricant in the spinning process “Shouprene” (registered trademark) 115: chloroprene rubber latex (available from Showa Denko K.K., surface tension: 47 mN/m, average particle size: 300 nm) “Nipol” (registered trademark) LX-111NF: polybutadiene rubber latex (available from Zeon Corporation, average particle size: 350 nm) “Nipol” (registered trademark) 2518FS: vinylpyridine-styrene-butadiene rubber latex (available from Zeon Corporation) “Nipol” (registered trademark) LX-517B: acrylonitrile-butadiene rubber latex (available from Zeon Corporation)

In Example 2, the relaxation of −6% was replaced with a stretching of 0% to a total stretching rate of 0%.

As can be seen from the evaluation results shown in Tables 2 and 3, the polyester fiber cord for reinforcing rubber according to the present invention has excellent adhesion to EPDM rubber and good processability. 

1-11. (canceled)
 12. A polyester fiber cord for reinforcing rubber comprising: a polyester fiber preloaded with a polyepoxide compound; and an adhesive applied to the polyester fiber and comprising a resorcinol-formalin-rubber latex (A), a blocked polyisocyanate compound (B), and a halogenated phenol derivative (C), wherein a rubber latex, a material of the resorcinol-formalin-rubber latex (A) in the adhesive, contains a mixture of a chloroprene rubber latex (D) and a polybutadiene rubber latex (E) in an amount of 80 to 100 parts by mass based on 100 parts by mass of the total solids of the rubber latex, and a mixing ratio of the chloroprene rubber latex (D) to the polybutadiene rubber latex (E) ((D)/(E)) is 80/20 to 20/80 (solid content mass ratio).
 13. The polyester fiber cord according to claim 12, wherein the chloroprene rubber latex (D) has a surface tension of 30 to 44 mN/m and an average particle size of 50 to 200 nm.
 14. The polyester fiber cord according to claim 12, wherein the polybutadiene rubber latex (E) has an average particle size of 200 to 330 nm.
 15. The polyester fiber cord according to claim 12, wherein the polyester fiber preloaded with a polyepoxide compound has an amorphism degree of orientation (fa) of 0.45 to 0.65.
 16. The polyester fiber cord according to claim 12, obtained by a single bath process where the polyester fiber preloaded with a polyepoxide compound is provided with the adhesive and then subjected to drying/heat treatment, wherein a total stretching rate in the drying/heat treatment is −10% to −4%.
 17. The polyester fiber cord according to claim 12, wherein a resorcin-formaldehyde precondensate contained in the resorcinol-formalin-rubber latex (A) is a novolac-type condensate.
 18. The polyester fiber cord according to claim 12, wherein the adhesive satisfies: (A)/(B)=5/1 to 20/1, (A)/(C)=1/1 to 5/1 (wherein (A) represents the amount of the resorcinol-formalin-rubber latex; (B) represents the amount of the blocked polyisocyanate compound; and (C) represents the amount of the halogenated phenol derivative, the ratios both representing a blend ratio by solid content mass).
 19. The polyester fiber cord according to claim 12, wherein the deposited amount of solid content of the adhesive on the polyester fiber preloaded with a polyepoxide compound is 1 to 5% by mass based on 100% by mass of the polyester fiber preloaded with a polyepoxide compound.
 20. The polyester fiber cord according to claim 12, which is a cord for reinforcing an automotive hose.
 21. The polyester fiber cord according to claim 12, wherein in the automotive hose, at least a portion in contact with the polyester fiber cord is an ethylene-α-olefin-unconjugated diene rubber formulation.
 22. A method of producing a polyester fiber cord comprising providing a polyester fiber preloaded with a polyepoxide compound with an adhesive comprising a resorcinol-formalin-rubber latex (A), a blocked polyisocyanate compound (B), and a halogenated phenol derivative (C), wherein a rubber latex, a component of the adhesive, contains a mixture of a chloroprene rubber latex (D) and a polybutadiene rubber latex (E) in an amount of 80 to 100 parts by mass based on 100 parts by mass of the total solids of the rubber latex, and a mixing ratio of the chloroprene rubber latex (D) to the polybutadiene rubber latex (E) ((D)/(E)) is from 80/20 to 20/80 (solid content mass ratio).
 23. The polyester fiber cord according to claim 13, wherein the polybutadiene rubber latex (E) has an average particle size of 200 to 330 nm.
 24. The polyester fiber cord according to claim 13, wherein the polyester fiber preloaded with a polyepoxide compound has an amorphism degree of orientation (fa) of 0.45 to 0.65.
 25. The polyester fiber cord according to claim 14, wherein the polyester fiber preloaded with a polyepoxide compound has an amorphism degree of orientation (fa) of 0.45 to 0.65.
 26. The polyester fiber cord according to claim 13, obtained by a single bath process where the polyester fiber preloaded with a polyepoxide compound is provided with the adhesive and then subjected to drying/heat treatment, wherein a total stretching rate in the drying/heat treatment is −10% to −4%.
 27. The polyester fiber cord according to claim 14, obtained by a single bath process where the polyester fiber preloaded with a polyepoxide compound is provided with the adhesive and then subjected to drying/heat treatment, wherein a total stretching rate in the drying/heat treatment is −10% to −4%.
 28. The polyester fiber cord according to claim 15, obtained by a single bath process where the polyester fiber preloaded with a polyepoxide compound is provided with the adhesive and then subjected to drying/heat treatment, wherein a total stretching rate in the drying/heat treatment is −10% to −4%.
 29. The polyester fiber cord according to claim 13, wherein a resorcin-formaldehyde precondensate contained in the resorcinol-formalin-rubber latex (A) is a novolac-type condensate.
 30. The polyester fiber cord according to claim 14, wherein a resorcin-formaldehyde precondensate contained in the resorcinol-formalin-rubber latex (A) is a novolac-type condensate.
 31. The polyester fiber cord according to claim 15, wherein a resorcin-formaldehyde precondensate contained in the resorcinol-formalin-rubber latex (A) is a novolac-type condensate. 